FTP the htaccess file to your server,but keep in mind that change the name to something else first and rename it when you've uploaded it.
If your host doesn't accept .htaccess files, then it seems the PHP is compiled as CGI in your server. You would be able to use php.ini file instead of .htaccess. Please let us know the exact thing you wanted to add with .htaccess files so that we could help you.
Thats exactly what I did. At my previous hosting I had to use .htaccess to get some pages to load properly. But at my new hosting .htaccess when uploaded completely knackered access to the pages. I had a look in my root dir and found a php.ini with the same text as the .htaccess but with the values of OFF. I set these to ON and all was well.